Residency · Residency · Cardiothoracic Surgery

Transcatheter Mitral Valve Interventions

Introduction

Transcatheter mitral valve interventions represent a rapidly evolving frontier in structural heart disease. These procedures offer therapeutic options for patients with severe mitral regurgitation (MR) who are deemed high-risk or inoperable for conventional surgical repair or replacement. The growing armamentarium of transcatheter devices addresses both primary (degenerative) and secondary (functional) mitral valve pathology.

Anatomy and Pathophysiology of Mitral Regurgitation

Mitral Valve Complex

The mitral valve apparatus consists of the annulus, anterior and posterior leaflets, chordae tendineae, and papillary muscles. Normal valve area is 4-6 cm2, and the coaptation zone requires at least 2 mm of leaflet overlap. The Carpentier classification guides surgical and interventional planning: Type I involves normal leaflet motion (annular dilation, perforation), Type II involves excessive leaflet motion (prolapse, flail), Type IIIa involves restricted motion in systole and diastole (rheumatic), and Type IIIb involves restricted motion in systole only (ischemic/functional).

Primary vs. Secondary MR

Primary MR involves intrinsic leaflet pathology from myxomatous degeneration, fibroelastic deficiency, or endocarditis. Secondary MR involves structurally normal leaflets with regurgitation caused by left ventricular dilation or dysfunction, annular dilation, or papillary muscle displacement. Secondary MR carries a worse prognosis and is more challenging to treat percutaneously.

Transcatheter Therapeutic Approaches

Edge-to-Edge Repair (MitraClip / TEER)

Transcatheter edge-to-edge repair (TEER) mimics the Alfieri stitch technique. The MitraClip device is delivered via transseptal puncture and grasps both leaflets to create a double-orifice valve. The COAPT trial demonstrated significant mortality and heart failure hospitalization benefit in secondary MR with appropriate patient selection. In contrast, the MITRA-FR trial showed neutral results, highlighting the importance of the proportionality concept (regurgitant volume relative to LV end-diastolic volume). Complications include clip detachment (1-2%), mitral stenosis, and pericardial tamponade.

Transcatheter Mitral Valve Replacement (TMVR)

TMVR addresses anatomies unsuitable for repair, including those with severe calcification, short leaflets, or failed prior repair. Devices include the Tendyne, EVOQUE, and Intrepid systems. Access routes include transapical, transseptal, or transatrial approaches. The key challenge is left ventricular outflow tract (LVOT) obstruction due to the anterior mitral leaflet being displaced by the prosthesis. Neo-LVOT assessment by CT imaging is critical, as an area below 200 mm2 predicts significant obstruction. Intentional laceration of the anterior mitral leaflet (LAMPOON) may be performed to mitigate LVOT obstruction.

Annuloplasty Devices

Percutaneous annuloplasty systems aim to reduce annular dimensions and restore coaptation. The Cardioband is a direct annuloplasty ring delivered transseptally and anchored to the posterior annulus. The Carillon provides indirect annuloplasty via a coronary sinus device that applies tension to the posterior annulus. The risk of coronary artery compromise from left circumflex proximity must be assessed.

Patient Selection and Imaging

Multimodality Imaging

Transesophageal echocardiography (TEE) is essential for procedural guidance and MR quantification. Cardiac CT provides annular sizing, neo-LVOT prediction, and access route planning. Cardiac MRI offers accurate regurgitant volume quantification when echocardiographic findings are discordant. Heart Team assessment integrating imaging, clinical status, and comorbidities guides decision-making.

Eligibility Criteria

Eligible patients have symptomatic severe MR (grade 3+ or 4+) despite guideline-directed medical therapy, high or prohibitive surgical risk (STS score, frailty, comorbidities), favorable anatomy for the chosen device (adequate leaflet length, suitable annular dimensions), and life expectancy above 1 year with expected quality of life improvement.

Outcomes and Complications

TEER achieves MR reduction to moderate or less in approximately 90-95% of cases. One-year mortality ranges from 15-25% in high-risk populations, reflecting baseline disease burden. Common complications include vascular access injury, transseptal complications, residual atrial septal defect, and device embolization. Long-term durability data for TMVR devices remain limited, and valve thrombosis and paravalvular leak require surveillance.

Key Clinical Pearls

The COAPT trial's success versus MITRA-FR's neutral outcome underscores that patient selection based on proportionate MR is critical for TEER benefit. The neo-LVOT area must always be assessed on CT before TMVR, and LAMPOON should be considered if obstruction is predicted. TEER is not a substitute for surgical repair in low-risk patients with primary MR and favorable anatomy. Heart Team collaboration between interventional cardiologists and cardiac surgeons is essential for optimal outcomes. Residual MR after TEER correlates with worse long-term outcomes, and the aim should be MR 1+ or less.

References

1. Stone GW, Lindenfeld J, Abraham WT, et al. Transcatheter Mitral-Valve Repair in Patients with Heart Failure. N Engl J Med. 2018;379(24):2307-2318.
2. Obadia JF, Messika-Zeitoun D, Leurent G, et al. Percutaneous Repair or Medical Treatment for Secondary Mitral Regurgitation. N Engl J Med. 2018;379(24):2297-2306.
3. Sorajja P, Moat N, Badhwar V, et al. Initial Feasibility Study of a New Transcatheter Mitral Prosthesis: The First 100 Patients. J Am Coll Cardiol. 2019;73(11):1250-1260.
4. Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. Circulation. 2021;143(5):e72-e227.

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